ReverendCharles
on the road
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I foamed all of the gaps in the floor around heat and water lines, will this cause a problem with the return air to the furnace? My tt has the Artic package with a sealed underbelly and a 4” heat duct to the belly. The belly is sealed with foam and has no cracks or gaps under the tt. How will the furnace get makeup air?
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robatthelake
Vancouver Island
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From the Outside air Intake!
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ReverendCharles
on the road
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I thought the outside intake was for combustion only, I am asking about return air makeup.
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old guy
Oregon (pronounced Or e gun)
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you should have a large paneled opening in front of the furnace. so long as you don't block that opening you will be alright
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fordsooperdooty
Southern California
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It would take a long time to burn up all the oxygen that you breath inside even the tightest sealed RV, and as said the combustion air comes from the exterior.
Just make sure to have a workibg CO alarm, and don't keep the doors shut too much, the moisture build up inside will get it pretty "humid" in there, what with the cooking, bathing and washing dishes...your walls and windows will be dripping condensation.
My posts shouldn't be taken for factual data. They are purely fictional, for entertainment purposes and should not be constituted as actually related to scientific, technical, engineering, legal, spiritual or practical advice. Amen. 
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Jim Cindy
Northcentral, PA
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ReverendCharles,
I think you are talking about a return air duct from the belly area of your TT. The arctic package insulates the very outside of the trailer. I doubt if the whole floor is sealed tightly enough to prevent a return air flow to the furnace. The duct to the belly forces hot air to that area. Without the duct, the basement would be not get enough heat to prevent freezing.
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Chris Bryant
DeLand, Florida, USA
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Assumption- the furnace is not located in the belly.
If you sealed it well enough, basically you won't get any heated air in to the belly.
-- Chris Bryant
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Old-Biscuit
Across the USA
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Joined: 06/20/2009
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Two different air flow systems
Combustion air....supplied from outside. Cooler air is 'pulled' in to burner area for combustion and then exhausted back outside
And
Warmed circulated air.......furnace blower discharges air thru registers into inside of rig. Then that air is returned to furnace for reheating and repeats cycle. (No different than A/C system except for cooling vs heating)
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skipnchar
Topeka or somewhere else
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Joined: 12/17/2003
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The cold air return is behind a grate where your furnace is located inside the RV. Sealing the belly makes no difference as it is essentially a closed system and does NOT draw air from outside.
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sum1
So-Cal
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Like Jim Cindy, I understand your question to be a concern for replacement for air lost from within the "cabin" since some of that air is going into the "belly". Your thinking is sound. And yes, combustion air should be drawn separately from outside.
If the belly is open to the outside by way of cracks and other leaks, you may indeed create a negative pressure in the cabin. This typically will be partially equalized by sucking air from every little leak in the cabin. Windows, doors, fixtures, etc.
If the belly is truly sealed from the outside and to the cabin, it will not accept air and the negative pressure in the cabin will not be created. The belly may not be warmed, however. This sounds like what you have now.
If there is now a return air means from the belly, or if one can be created, all of the above is minimized. If you do create a return air circuit from the belly, I suggest placing it in or very near the furnace return.
Wanna take it a step further? Install an outside makeup air using a gravity or spring-loaded intake "valve" to the furnace return. This may actually create a positive pressure in the cabin and belly virtually eliminating drafts at windows, etc. Now we've really gone too far, but I have created such systems and the concept is commonplace in commercial buildings.
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